This invention relates to a displacement sensor for use with robot end effectors in tactile operations, and more particularly to an optical displacement transducer.
In modern technologies, it is most important to use a robot which is capable of determining object shape through contact. For this purpose various types of displacement type transducers have been used, such as electrical transducers, which use various instruments to measure displacement, force transducers, which use a pliable solid to vary a certain electrical current, or optical displacement sensors, which measure the amount of light deflected from an object to determine its position, the present invention relates to the last-mentioned type of the transducer, the optical displacement sensor, which utilizes tactile sensing, that is information received through touch.
Since the optical sensors use light to transport information, they offer many advantages over electrical transducers, such as high sensitivity, versatility in design, and a high immunity to electromagnetic interference. Some of the optical displacement sensors use fiber optics to transmit and receive light reflected by an object. In fiber optic sensors a light emitting diode is used to emit light, which is reflected to a phototransistor.
Optical displacement transducers are sometimes used for the quality control of machined parts. These transducers, in some cases, use an occultation, or shadow method to produce an image into a camera for comparison with a "master" image. Micro-switches based on this principle are often used on assembly lines to detect the passage of an object and to record the number of items produced. The tactile sensors use a pair of emitter/detector hands arranged in arrays of sensors, which move in pre-determined directions, either in three axial directions, six axial displacements, etc. Some of the known optical tactile sensors use fiber optic cables which cross at right angles. The grid pattern is formed, and the grid junction surfaces of the optic cables are abraded to radiate light out of the sides of the fiber optic cables.
It is also important to note that robot sensors, in which the optical sensors are used, can be classified into internal and external state sensors. Internal state sensors detect the robot's joint positions. These type sensors include potentiometers and encoders in the motor of the robots.
External state sensors interact directly with the robot's surroundings. The external sensors can be contact and non-contact. The contact sensors are the sensors that measure physical contact with an object. These sensors detect force, torque, and/or pressure. Non-contact sensors sense objects with vision, light beams, and sound.
The present invention relates to a type of a transducer for use with a contact force sensor in detecting displacement of surface contours through the use of light.